The present invention relates to a nonwoven material produced by hydroentanglement of a wet-laid or foam-formed fibre web.
Hydroentanglement or spunlacing is a technique which was introduced in the 1970's, see e.g. CA patent no. 841, 938. The method involves forming a fibre web, either wet-laid or dry-laid, whereafter the fibres are entangled, i.e. tangled together by means of very fine water jets under high pressure. A plurality of rows of waterjets are directed towards the fibre web which is supported by a moving wire (mesh). The entangled web is then dried. The fibres which are used in the material can be constituted by synthetic or regenerated staple fibres, e.g. polyester, polyamide, polypropylene, rayon or the like, by pulp fibres or by mixtures of pulp fibres and staple fibres. Spunlace materials can be produced with high quality at a reasonable cost and they present good absorption characteristics. They are used, inter alia, as wipes or cleaning cloths for household or industrial use, as disposable materials for health care, etc.
EP-A-0 483 816 describes the production of a wet-laid hydroentangled material based on 100% pulp fibres. A hydroentangled nonwoven material consisting of 100% pulp fibres may have insufficient strength properties for certain applications of use where the material is subjected to high loading in a wet condition.
In order to achieve high material strength, a mixing-in of fibres which are longer than the pulp fibres is required. It is therefore common, as mentioned above, to mix in a certain proportion of synthetic or regenerated staple fibres. The synthetic fibres which are used are produced essentially from raw materials originating from oil or natural gas. The combustion or the biological breaking-down of the nonwoven waste based on synthetic fibres contributes to the so-called "greenhouse effect" since the fossil-bound carbon is released in the form of carbon dioxide. From this aspect it would be an advantage to make use of plant fibres instead of synthetic fibres for nonwoven production since no fossil carbon is released upon combustion or biologically breaking-down the material containing plant fibres and/or pulp fibres.
Wet-laying of long hydrophillic cellulosic fibres is difficult since the low wet bending stiffness of the fibres and their flocking tendency give rise to materials with non-uniform fibre formation. The problem with non-uniform fibre formation is additionally increased if hydroentanglement is used as a binding method.
According to WO 91/08333, hydrophobic plant fibres can be wet-laid and bound by means of hydroentanglement, resulting in a hydrophillic nonwoven material. In this case the hydrophobic fibres maintain a large part of their bending stiffness during the wet-laying process, which allows a comparatively uniform fibre formation.